Short Tricks for Multiplication – Part 2

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Multiplication tricks are vital to calculate long and difficult multiplication problems quickly. These tricks are best applied when we have large digit numbers, but they are equally fit for small digit numbers. In this blog post, we will discuss math tricks for fast multiplication. However, you can find the first part here (Short Tricks for Multiplication – Part 1).

Few Important Terms

The multiplicand is the number that is being multiplied. The multiplier is the number that is multiplying the first number.

For example, in 55 × 30, 55 is the multiplicand and 30 is the multiplier.

Bases are the numbers starting with 1 and followed by any number of 0’s. For example, 10, 100, 1000, 10000, …

A base number must start with 1 and should be followed only by 0’s. They are the first number for those many digits. Like, 10 for two-digit numbers, 100 for three-digit numbers, and so on.

The complement of a number is the number obtained from subtracting the number to its nearest base. For example,

  • complement of 43 is 100 – 43 = 57;
  • complement of 729 is 1000 – 729 = 271.

Trick 2

Multiplication of a number by 5n, where n is a natural number

Following are the steps:

Step 1. Add n number of zeroes at the end of the given number, where n is the power of 5;

Step 2. Now, divide the resultant number by 2n (= 2power of 5), to get the multiplication result.

Solution. Here 25 = 52, so that the power of 5 is 2 (= n).

Step 1.        Now, add 2 zeros at the end of 54, so that it becomes 5400.

Step 2.        Now, divide 5400 by 22 (= 2n) = 4.

Hence, it becomes = 5400/4 = 1350.

Therefore, 54 ×125 is 1350.

Solution. Here 125 = 53, so that the power of 5 is 3 (= n).

Step 1.        Now, add 3 zeros at the end of 87, so that it becomes 87000.

Step 2.        Now, divide 87000 by 23 (= 2n) = 8.

Hence, it becomes = 87000/8 = 10875.

Therefore, 87 ×125 is 10875.

Solution. Here 625 = 54, so that the power of 5 is 4 (= n).

  • Step 1.        Now, add 4 zeros at the end of 817, so that it becomes 8170000.
  • Step 2.        Now, divide 8170000 by 24 (= 2n) = 16.

Hence, it becomes = 8170000/16 = 510625.

Therefore, 817 × 625 is 510625.

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